Convert femtometer to kilometer Online | Free Length Converter

Femtometer

A femtometer (fm) is a unit of length in the metric system, equal to one-quadrillionth of a meter (1 fm = 10⁻¹⁵ meters). It is also known as a fermi, named after the physicist Enrico Fermi. Femtometers are used to measure extremely small distances at the subatomic level, such as the size of protons, neutrons, and atomic nuclei. For example, the radius of a proton is about 0.84 femtometers. This unit is commonly used in nuclear physics and particle physics, but it's far too small for everyday measurements.

Kilometer

A kilometer (km) is a unit of length in the metric system, used to measure long distances. One kilometer equals 1,000 meters or about 0.62 miles. Kilometers are commonly used to measure distances between cities, in road signs, and in running or walking events. For example, a marathon is 42.195 kilometers long. The symbol for kilometer is "km". Most countries around the world use kilometers instead of miles for speed and distance, especially in transportation. Because it covers a large distance, the kilometer is not used for measuring small objects but is perfect for travel and mapping.